Photolithography apparatus and method and method for handling wafer

ABSTRACT

A method for adhering a reticle onto a top surface of a chuck is provided in accordance with some embodiments of the present disclosure. The method includes contacting a plurality of fibers on the top surface of the chuck with the reticle. The reticle is slid relative to the top surface of the chuck along a first direction to increase a contact area between the fibers and the reticle, such that the reticle is adhered to the fibers.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application Ser.No. 62/718,958, filed Aug. 14, 2018, which is herein incorporated byreference in its entirety.

BACKGROUND

In semiconductor integrated circuit (IC) industry, technologicaladvances in IC materials and design have produced generations of ICswhere each generation has smaller and more complex circuits than theprevious generation. In the course of IC evolution, functional density(i.e., the number of interconnected devices per chip area) has generallyincreased while geometry size (i.e., the smallest component (or line)that can be created using a fabrication process) has decreased. Thisscaling down process generally provides benefits by increasingproduction efficiency and lowering associated costs. Such scaling downhas also increased the complexity of IC processing and manufacturing.

A photolithography process forms a patterned resist layer for variouspatterning processes, such as etching or ion implantation. The minimumfeature size that may be patterned by way of such a photolithographyprocess is limited by the wavelength of the projected radiation source.Photolithography machines have gone from using ultraviolet light with awavelength of 365 nanometers to using deep ultraviolet (DUV) lightincluding a krypton fluoride laser (KrF laser) of 248 nanometers and anargon fluoride laser (ArF laser) of 193 nanometers, and to using extremeultraviolet (EUV) light of a wavelength of 13.5 nanometers, improvingthe resolution at every step.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a flow chart illustrating a photolithography method inaccordance with some embodiments of the instant disclosure;

FIG. 2 illustrates a cross-sectional view of a photolithographyapparatus in accordance with some embodiments of the instant disclosure;

FIG. 3 illustrates a top view of a reticle chuck of a photolithographyapparatus in accordance with some embodiments of the instant disclosure;

FIG. 4 illustrates a cross-sectional view of the reticle chuck with anadhesive layer thereon in accordance with some embodiments of theinstant disclosure;

FIG. 5 illustrates a top view of an intermediary stage of operating thephotolithography apparatus in accordance with some embodiments of theinstant disclosure;

FIGS. 6 through 8 illustrate cross-sectional views of intermediarystages of operating the photolithography apparatus in accordance withsome embodiments of the instant disclosure;

FIG. 9 illustrates a cross-sectional view of one fiber of the adhesivelayer in FIG. 4 in accordance with some embodiments of the instantdisclosure;

FIG. 10 illustrates a cross-sectional view of the reticle chuck with anadhesive layer thereon in accordance with some embodiments of theinstant disclosure;

FIG. 11 is a flow chart illustrating a method for handling a wafer inaccordance with some embodiments of the instant disclosure;

FIG. 12 illustrates a top view of a wafer handler with a wafer thereonin accordance with some embodiments of the instant disclosure;

FIG. 13 illustrates a cross-sectional view of the wafer handler inaccordance with some embodiments of the instant disclosure;

FIG. 14 illustrates a cross-sectional view of the wafer holder with anadhesive layer thereon in accordance with some embodiments of theinstant disclosure; and

FIGS. 15 through 16 illustrate cross-sectional views of intermediarystages of operating the wafer handler in accordance with someembodiments of the instant disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Silicon wafers are manufactured in a sequence of successive lithographysteps including mask alignment, exposure, photoresist development, layeretch, and epitaxial layer growth to form a pattern which defines devicestructures and interconnects within an integrated circuit (IC). Toguarantee robust mask alignment, dedicated alignment structures areplaced within physical layout data of the IC, and are utilized by anin-line alignment tool within a semiconductor manufacturing flow toachieve overlay (OVL) control during mask alignment. A patterned waferconsists of a plurality of ICs arranged into a periodic array or reticlefields, in which each reticle field is patterned by a step-and-repeattool configured to align a patterned mask to an individual reticle fieldbased on a wafer map of alignment structure locations obtained from thephysical layout data of the IC. Yield and device performance rely uponrobust OVL control between two or more mask alignment steps when forminglayers of a device.

As the lithography processes become more sophisticated, the OVL qualitybetween a reticle chuck and a mask needs to be improved. To improve theOVL quality, contact area between the reticle chuck and the mask mayneed to be increased. However, a large contact area leads to a large Vander Waals force, which may cause the difficulty of removing the maskfrom the reticle chuck. If the mask is forcibly removed, the reticlechuck may be damaged.

Reference is made to FIG. 1, a flow chart illustrating aphotolithography method 1000 in accordance with some embodiments of theinstant disclosure. The method 1000 begins with operation 1100 in whicha plurality of flexible or bendable fibers on a top surface of a chuckcontact a reticle (i.e., a mask). The method 1000 continues withoperation 1200 in which the reticle slides relative to the top surfaceof the chuck along a first direction to increase a contact area betweenthe fibers and the reticle, such that the reticle is adhered to thefibers. Subsequently, operation 1300 is performed. A photolithographyprocess is performed using the reticle secured on the reticle chuck. Themethod 1000 continues with operation 1400 in which the reticle slidesrelative to the top surface of the chuck along a second direction thatis opposite to the first direction to decrease a contact area betweenthe fibers and the reticle. The method 1000 continues with operation1500 in which the reticle is detached from the fibers. The discussionthat follows illustrates embodiments of a photolithography apparatusthat can be operated according to the method 1000 of FIG. 1. Whilemethod 1000 is illustrated and described below as a series of actions orevents, it will be appreciated that the illustrated ordering of suchactions or events are not to be interpreted in a limiting sense. Forexample, some actions may occur in different orders and/or concurrentlywith other actions or events apart from those illustrated and/ordescribed herein. In addition, not all illustrated actions may berequired to implement one or more aspects or embodiments of thedescription herein. Further, one or more of the actions depicted hereinmay be carried out in one or more separate actions and/or phases.

Reference is made to FIG. 2. FIG. 2 illustrates a cross-sectional viewof a photolithography apparatus 100 in accordance with some embodimentsof the instant disclosure. The apparatus 100 includes a reticle chuck110, an adhesive layer 130, a light source 150, a baffle 160, objectivelenses 170 a, 170 b, and a wafer stage 180. The reticle chuck 110 isconfigured to temporarily secure a reticle 121 of a mask system 120using the adhesive layer 130. That is, the reticle chuck 110 is a kindof workpiece holding device. The light source 150 is over the reticlechuck 110. The baffle 160 is between the reticle chuck 110 and the lightsource 150 and has an exposure slit 161. The light source 150 isconfigured to emit light toward the reticle chuck 110 through theexposure slit 161. The objective lens 170 a is between the baffle 160and the reticle chuck 110 and configured to focus the light emitted bythe light source 150 onto the reticle 121. The wafer stage 180 is underthe reticle chuck 110 and configured to support a wafer W thereon. Theobjective lens 170 b is between the wafer stage 180 and the reticlechuck 110 and configured to focus the light passing through the reticle121 onto the wafer W. The apparatus 100 is configured to perform asemiconductor photolithography process of transferring patterns ofgeometric shapes on the reticle 121 to a thin layer of photosensitivematerial (called photoresist) covering the surface of the wafer W. Thatis, the primary exposure method used by the apparatus 100 is projectionprinting, but the disclosure is not limited in this regard. In someembodiments, the apparatus 100 uses a type of stepper called a scanner,which moves the wafer stage 180 and reticle chuck 110 with respect toeach other during the exposure, as a way of increasing the size of theexposed area and increasing the imaging performance of the objectivelenses 170 a, 170 b.

Reference is made to FIGS. 3 and 4. FIG. 3 illustrates a top view of thereticle chuck 110 of the apparatus 100 in accordance with someembodiments of the instant disclosure. FIG. 4 illustrates across-sectional view of the reticle chuck 110 with an adhesive layer 130thereon in accordance with some embodiments of the instant disclosure.The reticle chuck 110 has a first top surface 111. The adhesive layer130 is present on the first top surface 111 and includes a plurality offibers 131. In some embodiments, the adhesive layer 130 is polymer-baseddry adhesives or carbon nanotube (CNT)-based dry adhesives. In otherwords, the fibers 131 may be nano-scaled structures.

In some embodiments as shown in FIG. 4, each of the fibers 131 has afirst end 131 a and a second end 131 b. The first end 131 a is connectedto the first top surface 111 of the reticle chuck 110, in which a widthof the first end 131 a of each of the fibers 131 is greater than a widthof the second end 131 b. Specifically, as shown in FIG. 4, a width of atleast one of the fibers 131 is gradually reduced from the first end 131a to the second end 131 b of said at least one of the fibers 131. Thatis, said at least one of the fibers 131 tapers towards its top and isbased on bottom-up growth from the first end 131 a to the second end 131b like a conical pillar.

In some embodiments, a width of the fibers 131 is substantially in arange from about 0.2 μm to about 0.5 μm. Under the condition that thedistance between any two adjacent fibers 131 is constant, a width of thefibers 131 that is greater than about 0.5 μm may make the number offibers 131 per unit area too small (i.e., the molecular density may betoo small) and result in small Van der Waals forces, and a width of thefibers 131 that is smaller than about 0.2 μm may make the number offibers 131 per unit area too large (i.e., the molecular density may betoo large) and cause the fibers 131 to stick to each other, which mayworsen adsorption properties of the fibers 131.

In some embodiments, a height of the fibers 131 is substantially in arange from about 1.0 μm to about 1.5 μm. A height of the fibers 131 thatis greater than about 1.5 μm may increase the degree of clutter, whichmay make it difficult to control the inclination direction of the fibers131. A height of the fibers 131 that is smaller than about 1.0 μm mayreduce the contact area between the fibers 131 and the reticle 121,which may reduce the adsorption force of the fibers 131.

In some embodiments as shown in FIG. 4, the second end 131 b isconfigured to bend relative to the first end 131 a substantially along afirst direction A1 and not along a second direction A2 opposite to thefirst direction A1, in which the first direction A1 and the seconddirection A2 are substantially parallel to the first top surface 111 ofthe reticle chuck 110. In some embodiments, at least one of the fibers131 is originally inclined toward the first direction A1 relative to thefirst top surface 111 of the reticle chuck 110 when said at least one ofthe fibers 131 does not contact the bottom surface 121 a (referring toFIG. 7) of the reticle 121. In other words, the first end 131 a of saidat least one of the fibers 131 has a first side facing along the firstdirection A1 and a second side facing along the second direction A2, anda vertical projection of the second end 131 b of said at least one ofthe fibers 131 projected onto the first top surface 111 of the reticlechuck 110 is close to the first side of the first end 131 a and awayfrom the second side of the first end 131 a when said at least one ofthe fibers 131 does not contact the bottom surface 121 a of the reticle121. Specifically, as shown in FIG. 4, a distance D1 represents aminimum distance between the vertical projection of the second end 131 b(on the surface 111) and the first side of the first end 131 a, adistance D2 represents a minimum distance between the verticalprojection of the second end 131 b (on the surface 111) and the secondside of the first end 131 a, and the distance D1 is different fromdistance D2. In some embodiments, said at least one of the fibers 131originally inclines relative to the first top surface 111 of the reticlechuck 110 at an inclined angle α substantially smaller than about 80degrees when said at least one of the fibers 131 does not contact thebottom surface 121 a of the reticle 121. In some embodiments, theinclined angle αof said at least one of the fibers 131 is defined by anangle formed between the first top surface 111 of the reticle chuck 110and a connection line connecting the first end 131 a (e.g., a center ofthe first end 131 a) and the second end 131 b of said at least one ofthe fibers 131, for example.

FIG. 5 illustrates a top view of an intermediary stage of operating thephotolithography apparatus in accordance with some embodiments of theinstant disclosure. FIGS. 6 through 8 illustrate cross-sectional viewsof intermediary stages of operating the photolithography apparatus inaccordance with some embodiments of the instant disclosure. FIG. 6illustrates a partial cross-section taken along line I-I illustrated inFIG. 5. FIGS. 7 and 8 illustrate partial cross-sections taken along lineII-II illustrated in FIG. 5.

Reference is made to FIGS. 3, 5, and 6. As shown in FIG. 3, the reticlechuck 110 further has a second top surface 112. The second top surface112 is parallel to, substantially coplanar with, and spaced apart fromthe first top surface 111, and the adhesive layer 130 is further presenton the second top surface 112. As shown in FIGS. 5 and 6, the adhesivelayer 130 present on the first top surface 111 and the second topsurface 112 of a reticle chuck 110 contacts the bottom surface 121 a ofa reticle 121.

Reference is made to FIGS. 6 and 7. The adhesive layer 130 present onthe first top surface 111 and the second top surface 112 of the reticlechuck 110 contacts the bottom surface 121 a of the reticle 121. Afterthe adhesive layer 130 contacts the bottom surface 121 a, the bottomsurface 121 a of the reticle 121 slides relative to the first topsurface 111 and the second top surface 112 of the reticle chuck 110along the first direction A1, so as to increase a contact area betweenthe fibers 131 and the bottom surface 121 a of the reticle 121. At thesame time, at least one of the fibers 131 present on the first topsurface 111 inclines relative to the first top surface 111 at a firstinclined angle α1 and adheres to the bottom surface 121 a of the reticle121 with a first adhesive force. In some embodiments, after the reticle121 is secured onto the first top surface 111 and the second top surface112 of the reticle chuck 110, a photolithography process is performedusing the reticle 121.

In some embodiments as shown in FIG. 7, the first inclined angle α1 issubstantially in a range from about 0 degree to about 10 degrees. On theother hand, the second end 131 b of said at least one of the fibers 131bends relative to the first end 131 a substantially along the firstdirection A1 at the same time. In some embodiments, a bending angle ofsaid at least one of the fibers 131 as shown in FIG. 7 relative to saidat least one of the fibers 131 as shown in FIG. 4 is substantially in arange from about 70 degrees to about 80 degrees (i.e., the inclinedangle αminus the first inclined angle α1), but the disclosure is notlimited in this regard.

In some embodiments, in order to properly secure the reticle 121 ontothe reticle chuck 110, a height of the fibers 131 squeezed between thereticle 121 and the reticle chuck 110 is substantially in a range fromabout 0.5 μm to about 0.8 μm. A height of the squeezed fibers 131 thatis greater than about 0.8 μm may create a relatively small contact areaand thus result in a poor adsorption force, so the reticle 121 is proneto falling from the reticle chuck 110. A height of the squeezed fibers131 that is smaller than about 0.5 μm may make the molecular density ofthe fibers 131 too large and cause the fibers 131 to stick to eachother, which may worsen adsorption properties of the fibers 131 and makethe reticle 121 prone to falling from the reticle chuck 110.

In some embodiments as shown in FIG. 6, the reticle 121 includes asubstrate and a patterned layer that defines an integrated circuit to betransferred to a semiconductor substrate (e.g., the wafer shown in FIG.2) during the photolithography process. The reticle 121 is typicallyincluded with a pellicle assembly 122, collectively referred to as theaforementioned mask system 120. The pellicle assembly 122 includes atransparent thin membrane 122 a and a pellicle frame 122 b. The pellicleframe 122 b is mounted on the bottom surface 121 a of the reticle 121.The transparent thin membrane 122 a is mounted over the pellicle frame122 b. The pellicle assembly 122 protects the reticle 121 from fallenparticles and keeps the particles out of focus so that they do notproduce a patterned image, which may cause defects when the reticle 121is being used. The transparent thin membrane 122 a is typicallystretched and mounted over the pellicle frame 122 b, and is attached tothe pellicle frame 122 b by glue or other adhesives.

In some embodiments, the first top surface 111 and the second topsurface 112 substantially extend along the first direction A1 and thesecond direction A2, and are arranged with respect to each other in athird direction A3 inclined relative to the first direction A1 and thesecond direction A2. In some embodiments, the third direction A3 isperpendicular to the first direction A1 and the second direction A2, butthe disclosure is not limited in this regard. As shown in FIGS. 5 and 6,two opposite side edges of the reticle 121 are respectively supported onthe first top surface 111 and the second top surface 112 of the reticlechuck 110. Meanwhile, the pellicle assembly 122 of the mask system 120extends between and is spaced apart from the first top surface 111 andthe second top surface 112. In this way, the pellicle assembly 122 willnot collide with the reticle chuck 110 when the bottom surface 121 a ofthe reticle 121 slides relative to the first top surface 111 and thesecond top surface 112 along the first direction A1.

In some embodiments as shown in FIG. 3, the reticle chuck 110 has aplurality of vacuum holes 113. Each of the vacuum holes 113 iscommunicated to one of the first top surface 111 and the second topsurface 112. The apparatus 100 further includes a vacuum source 140. Thevacuum source 140 is in fluid communication with the plurality of vacuumholes 113 and is configured to form a low pressure vacuum between thefirst top surface 111 and the bottom surface 121 a of the reticle 121and between the second top surface 112 and the bottom surface 121 athrough the vacuum holes 113 when the bottom surface 121 a covers thevacuum holes 113. Each of the vacuum holes 113 of the reticle chuck 110is surrounded by the fibers 131.

In some embodiments, the vacuum source 140 form the low pressure vacuumbetween the first top surface 111 and the bottom surface 121 a andbetween the second top surface 112 and the bottom surface 121 a throughthe vacuum holes 113 after the bottom surface 121 a of the reticle 121slides relative to the first top surface 111 and the second top surface112 along the first direction A1 and before the photolithography processis performed. In some other embodiments, the vacuum source 140 form thelow pressure vacuum between the first top surface 111 and the bottomsurface 121 a and between the second top surface 112 and the bottomsurface 121 a through the vacuum holes 113 after the adhesive layer 130present on the first top surface 111 and the second top surface 112 ofthe reticle chuck 110 contacts the bottom surface 121 a of the reticle121 and before the bottom surface 121 a slides relative to the first topsurface 111 and the second top surface 112 along the first direction A1.

In some embodiments, the vacuum holes 113 on either the first topsurface 111 or the second top surface 112 are elongated along the thirddirection A3 and sequentially arranged in a line along the thirddirection A3, but the disclosure is not limited in this regard.

Reference is made to FIGS. 6 and 8. After the photolithography processis performed using the reticle 121, the bottom surface 121 a of thereticle 121 slides relative to the first top surface 111 and the secondtop surface 112 of the reticle chuck 110 along the second direction A2,so as to elevate the reticle 121 and decrease a contact area between thefibers 131 and the bottom surface 121 a of the reticle 121. At the sametime, at least one of the fibers 131 present on the first top surface111 inclines relative to the first top surface 111 at a second inclinedangle α2 and adheres to the bottom surface 121 a of the reticle 121 witha second adhesive force, in which the first adhesive force is greaterthan the second adhesive force. In some embodiments, the reticle chuck110 may include glass, quartz, a combination thereof, or the like. Insome embodiments, the reticle 121 may include glass, quartz, silicon,silicon carbide, black diamond, combinations thereof, or the like. Assuch, the reticle 121 of the mask system 120 can be then detached fromthe reticle chuck 110 under a smaller adhesive force produced by theadhesive layer 130, so that the reticle 121 and the reticle chuck 110can be effectively prevented from breakage during detaching. In someembodiments as shown in FIGS. 7 and 8, the first inclined angle α1 issmaller than the second inclined angle α2.

In other words, by sliding the bottom surface 121 a of the reticle 121relative to the first top surface 111 and the second top surface 112 ofthe reticle chuck 110 substantially along the first direction A1, theVan der Waals force produced between the adhesive layer 130 and thebottom surface 121 a of the reticle 121 can be increased, so as toeffectively improve the OVL quality between the reticle chuck 110 andthe reticle 121. By sliding the bottom surface 121 a of the reticle 121relative to the first top surface 111 and the second top surface 112 ofthe reticle chuck 110 substantially along the second direction A2, theVan der Waals force produced between the adhesive layer 130 and thebottom surface 121 a of the reticle 121 can be decreased, so as toeasily detach the reticle 121 from the reticle chuck 110 withoutbreaking the reticle chuck 110.

In some embodiments as shown in FIG. 8, the second inclined angle α2 issubstantially in a range from about 30 degrees to about 80 degrees. Atthe same time, the second end 131 b of said at least one of the fibers131 still bends relative to the first end 131 a substantially along thefirst direction A1. In some embodiments, a bending angle of said atleast one of the fibers 131 as shown in FIG. 8 relative to said at leastone of the fibers 131 as shown in FIG. 4 is substantially in a rangefrom about 0 degree to about 50 degrees (i.e., the inclined angle αminusthe second inclined angle α2), but the disclosure is not limited in thisregard.

In some embodiments with the vacuum source 140 forming the low pressurevacuum between the first top surface 111 and the bottom surface 121 aand between the second top surface 112 and the bottom surface 121 athrough the vacuum holes 113 before the photolithography process isperformed, the low pressure vacuum can be removed by controlling thevacuum source 140 after the bottom surface 121 a slides relative to thefirst top surface 111 and the second top surface 112 along the seconddirection A2 and before the reticle 121 of the mask system 120 isdetached from the reticle chuck 110. In some other embodiments, the lowpressure vacuum can be removed by controlling the vacuum source 140after the photolithography process is performed and before the bottomsurface 121 a slides relative to the first top surface 111 and thesecond top surface 112 along the second direction A2.

Reference is made to FIG. 9. FIG. 9 illustrates a cross-sectional viewof one of the fibers 131 of the adhesive layer 130 in FIG. 4 inaccordance with some embodiments of the instant disclosure, in which across-section of said one of the fibers 131 is taken along line III-III.In some embodiments as illustrated in FIG. 9, the cross-section of saidone of the fibers 131 is parallel to the first top surface 111 of thereticle chuck 110 and is noncircular. For example, a width of thecross-section in a direction inclined relative to the first direction A1is greater than a width of the cross-section in the first direction A1,so that the second end 131 b of said one of the fibers 131 is apt tobend relative to the first end 131 a substantially along the firstdirection A1. In some embodiments, the cross-section has a largest widthin a direction perpendicular to the first direction A1 and has asmallest width in the first direction A1, but the disclosure is notlimited in this regard.

Reference is made to FIG. 10. FIG. 10 illustrates a cross-sectional viewof a reticle chuck 110 with an adhesive layer 230 thereon in accordancewith some embodiments of the instant disclosure. The adhesive layer 230is present on the first top surface 111 and includes a plurality offibers 231. In some embodiments, the adhesive layer 230 is polymer-baseddry adhesives or CNT-based dry adhesives. In other words, the fibers 231may be nano-scaled structures. In some embodiments, each of the fibers231 has a first end 231 a and a second end 231 b. The first end 231 a isconnected to the first top surface 111 of the reticle chuck 110. In someother embodiments, at least one of the fibers 231 substantially has auniform width. In other words, in such embodiments, the first end 231 aand the second end 231 b of said at least one of the fibers 231substantially have the same width, and said at least one of the fibers231 is based on bottom-up growth from the first end 231 a to the secondend 231 b like a straight pillar.

Reference is made to FIG. 11, a flow chart illustrating a method 3000for handling a wafer in accordance with some embodiments of the instantdisclosure. The method 3000 begins with operation 3100 in which aplurality of fibers on a top surface of a wafer holder contacts a wafer.The method 3000 continues with operation 3200 in which the wafer holderslides relative to the wafer along a first direction to incline thefibers relative to the top surface of the wafer holder, such that thewafer is adhered to the fibers. The method 3000 continues with operation3300 in which the wafer moves to a carrier using a robot to drive amechanical arm connected to the wafer holder. The method 3000 continueswith operation 3400 in which the wafer holder slides relative to thewafer along a second direction that is opposite to the first directionto decrease a contact area between the fibers and the wafer. The method3000 continues with operation 3500 in which the wafer holder is detachedfrom the wafer to leave the wafer on the carrier. The discussion thatfollows illustrates embodiments of a photolithography apparatus that canbe operated according to the method 3000 of FIG. 11. While method 3000is illustrated and described below as a series of actions or events, itwill be appreciated that the illustrated ordering of such actions orevents are not to be interpreted in a limiting sense. For example, someactions may occur in different orders and/or concurrently with otheractions or events apart from those illustrated and/or described herein.In addition, not all illustrated actions may be required to implementone or more aspects or embodiments of the description herein. Further,one or more of the actions depicted herein may be carried out in one ormore separate actions and/or phases.

Reference is made to FIGS. 12 and 13. FIG. 12 illustrates a top view ofa wafer handler 300 with a wafer W thereon in accordance with someembodiments of the instant disclosure. FIG. 13 illustrates across-sectional view of the wafer handler 300 taken along line IV-IVillustrated in FIG. 12 in accordance with some embodiments of theinstant disclosure. The wafer handler 300 includes a wafer holder 310,an adhesive layer 320, a robot 330, and a mechanical arm 340. The waferholder 310 has a top surface 310 a configured to carry a wafer Wthereon. That is, the wafer holder 310 is a kind of workpiece holdingdevice. The wafer holder 310 is constructed of a blade portion 311, apair of object sensors 312 a, 312 b mounted in the top surface 310 a,and a printed circuit board 313 for controlling the object sensors 312a, 312 b. The object sensors 312 a, 312 b are utilized to sense thepresence of the wafer W which is properly positioned on the bladeportion 311. The adhesive layer 320 is present on the top surface 310 aof the wafer holder 310 and includes a plurality of fibers 321. In someembodiments, the adhesive layer 320 is polymer-based dry adhesives orcarbon nanotube (CNT)-based dry adhesives. In other words, the fibers321 are nano-scaled structures. The mechanical arm 340 is connectedbetween the robot 330 and the wafer holder 310. The robot 330 isconfigured to drive the mechanical arm 340 to move the wafer holder 310away from the robot 330 along a first direction A1 and configured todrive the mechanical arm 340 to move the wafer holder 310 toward therobot 330 along a second direction A2 opposite to the first directionA1. In some embodiments, the first direction A1 and the second directionA2 are substantially parallel to the top surface 310 a of the waferholder 310.

Reference is made to FIG. 14. FIG. 14 illustrates a cross-sectional viewof the wafer holder 310 with the adhesive layer 320 thereon taken alongline V-V illustrated in FIG. 12 in accordance with some embodiments ofthe instant disclosure. In some embodiments as shown in FIG. 14, each ofthe fibers 321 has a first end 321 a and a second end 321 b. The firstend 321 a is connected to the top surface 310 a of the wafer holder 310,in which width of the first end 321 a of each of the fibers 321 isgreater than a width of the second end 321 b. Specifically, as shown inFIG. 14, widths of at least one of the fibers 321 are gradually reducedfrom the first end 321 a to the second end 321 b of said at least one ofthe fibers 321. That is, said at least one of the fibers 321 taperstowards its top and is based on bottom-up growth from the first end 321a to the second end 321 b like a conical pillar.

In some embodiments, a width of the fibers 321 is substantially in arange from about 0.2 μm to about 0.5 μm. Under the condition that thedistance between any two adjacent fibers 321 is constant, a width of thefibers 321 that is greater than about 0.5 μm may make the number offibers 321 per unit area too small (i.e., the molecular density may betoo small) and result in small Van der Waals forces, and a width of thefibers 321 that is smaller than about 0.2 μm may make the number offibers 321 per unit area too large (i.e., the molecular density may betoo large) and cause the fibers 321 to stick to each other, which mayworsen adsorption properties of the fibers 321.

In some embodiments, a height of the fibers 321 is substantially in arange from about 1.0 μm to about 1.5 μm. A height of the fibers 321 thatis greater than about 1.5 μm may increase the degree of clutter, whichmay make it difficult to control the inclination direction of the fibers321. A height of the fibers 321 that is smaller than about 1.0 μm mayreduce the contact area between the fibers 321 and the wafer W, whichmay reduce the adsorption force of the fibers 321.

In some other embodiments, at least one of the fibers 321 substantiallyhas a uniform width like the fiber 131 shown in FIG. 10. In other words,in such embodiments, the first end 321 a and the second end 321 b ofsaid at least one of the fibers 321 substantially have the same width,and said at least one of the fibers 321 is based on bottom-up growthfrom the first end 321 a to the second end 321 b like a straight pillar.

In some embodiments as shown in FIG. 14, the second end 321 b isconfigured to bend relative to the first end 321 a substantially alongthe second direction A2 and not along the first direction A1. In someembodiments, at least one of the fibers 321 is originally inclinedtoward the second direction A2 relative to the top surface 310 a of thewafer holder 310 when said at least one of the fibers 321 does notcontact the wafer W. In other words, the first end 321 a of said atleast one of the fibers 321 has a first side facing along the firstdirection A1 and a second side facing along the second direction A2, anda vertical projection of the second end 321 b of said at least one ofthe fibers 321 projected onto the top surface 310 a of the wafer holder310 is close to the second side of the first end 321 a and away from thefirst side of the first end 321 a when said at least one of the fibers321 does not contact the wafer W. In some embodiments, said at least oneof the fibers 321 originally inclines relative to the top surface 310 aof the wafer holder 310 at an inclined angle αsubstantially smaller thanabout 80 degrees when said at least one of the fibers 321 does notcontact the wafer W. In some embodiments, the inclined angle αof said atleast one of the fibers 321 is defined by an angle formed between thetop surface 310 a of the wafer holder 310 and a connection lineconnecting the first end 321 a (e.g., a center of the first end 321 a)of the second end 321 b of said at least one of the fibers 321, forexample.

In some embodiments, a cross-section of at least one of the fibers 321parallel to the top surface 310 a of the wafer holder 310 is noncircularlike the cross-section of the fiber 131 shown in FIG. 9. For example, awidth of the cross-section in a direction inclined relative to thesecond direction A2 is greater than a width of the cross-section in thesecond direction A2, so that the second end 321 b of said at least oneof the fibers 321 is apt to bend relative to the first end 321 asubstantially along a second direction A2. In some embodiments, thecross-section has a largest width in a direction perpendicular to thesecond direction A2 and has a smallest width in the second direction A2,but the disclosure is not limited in this regard.

FIGS. 15 through 16 illustrate cross-sectional views of intermediarystages of operating the wafer handler 300 in accordance with someembodiments of the instant disclosure. FIGS. 15 and 16 illustratepartial cross-sections taken along line V-V illustrated in FIG. 12.

Reference is made to FIGS. 14 and 15. The adhesive layer 320 present onthe top surface 310 a of the wafer holder 310 contacts the wafer W.After the adhesive layer 320 contacts the wafer W, the top surface 310 aof the wafer holder 310 slides relative to the wafer W along the firstdirection A1, so as to increase a contact area between the fibers 321and the wafer W. At the same time, at least one of the fibers 321present on the top surface 310 a inclines relative to the top surface310 a at a first inclined angle α1 and adheres to the wafer W with afirst adhesive force. In some embodiments, after the wafer W is securedonto the top surface 310 a of the wafer holder 310, the wafer W is movedto a carrier using the robot 330 to drive the mechanical arm 340connected to the wafer holder 310. In some embodiments, the carrier is acassette pod or an electrostatic chuck in a processing chamber, forexample.

In some embodiments as shown in FIG. 15, the first inclined angle α1 issubstantially in a range from about 0 degree to about 10 degrees. On theother hand, the second end 321 b of said at least one of the fibers 321bends relative to the first end 321 a substantially along the seconddirection A2 at the same time. In some embodiments, a bending angle ofsaid at least one of the fibers 321 as shown in FIG. 15 relative to saidat least one of the fibers 321 as shown in FIG. 14 is substantially in arange from about 70 degrees to about 80 degrees (i.e., the inclinedangle α minus the first inclined angle α1), but the disclosure is notlimited in this regard.

In some embodiments, in order to properly secure the wafer W onto thewafer holder 310, a height of the fibers 321 squeezed between the waferW and the wafer holder 310 is substantially in a range from about 0.5 μmto about 0.8 μm. A height of the squeezed fibers 321 that is greaterthan about 0.8 μm may create a relatively small contact area and thusresult in a poor adsorption force, so the wafer W is prone to fallingfrom the wafer holder 310. A height of the squeezed fibers 321 smallerthan about 0.5 μm may make the molecular density of the fibers 321 toolarge and cause the fibers 321 to stick to each other, which may worsenadsorption properties of the fibers 321 and make the wafer W prone tofalling from the wafer holder 310.

Reference is made to FIGS. 14 and 16. After the wafer W is moved to thecarrier, the top surface 310 a of the wafer holder 310 slides relativeto the wafer W along the second direction A2, so as to decrease acontact area between the fibers 321 and the wafer W. At the same time,at least one of the fibers 321 present on the top surface 310 a inclinesrelative to the top surface 310 a at a second inclined angle α2 andadheres to the wafer W with a second adhesive force, in which the firstadhesive force is greater than the second adhesive force. As such, thewafer W can be then detached from the wafer holder 310 under a smalleradhesive force produced by the adhesive layer 320, so that the wafer Wcan be effectively prevented from breakage during detaching. In someembodiments as shown in FIGS. 15 and 16, the first inclined angle α1 issmaller than the second inclined angle α2.

In other words, by sliding the top surface 310 a of the wafer holder 310relative to the wafer W substantially along the first direction A1, theVan der Waals force produced between the adhesive layer 320 and thewafer W can be increased, so as to effectively improve the OVL qualitybetween the wafer holder 310 and the wafer W. By sliding the top surface310 a of the wafer holder 310 relative to the wafer W substantiallyalong the second direction A1, the Van der Waals force produced betweenthe adhesive layer 320 and the wafer W can be decreased, so as to easilydetach the wafer W from the wafer holder 310 without breaking the waferW.

In some embodiments as shown in FIG. 16, the second inclined angle α2 issubstantially in a range from about 30 degrees to about 80 degrees. Atthe same time, the second end 321 b of said at least one of the fibers321 still bends relative to the first end 321 a substantially along thesecond direction A2. In some embodiments, a bending angle of said atleast one of the fibers 321 as shown in FIG. 16 relative to said atleast one of the fibers 321 as shown in FIG. 14 is substantially in arange from about 0 degree to about 50 degrees, but the disclosure is notlimited in this regard.

In some embodiments, a method includes contacting a plurality of fiberson a top surface of a chuck with a reticle. The reticle is slid relativeto the top surface of the chuck along a first direction to increase acontact area between the fibers and the reticle, such that the reticleis adhered to the fibers.

In some embodiments, a method includes contacting a plurality of fiberson a top surface of a wafer holder with a wafer. The wafer holder isslid relative to the wafer along a first direction to incline the fibersrelative to the top surface of the wafer holder, such that the wafer isadhered to the fibers.

In some embodiments, an apparatus includes a workpiece holding deviceand a plurality of fibers. The fibers are on a top surface of theworkpiece holding device.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: contacting a plurality offibers on a top surface of a chuck with a reticle; and sliding thereticle relative to the top surface of the chuck along a first directionto increase a contact area between the fibers and the reticle, such thatthe reticle is adhered to the fibers.
 2. The method of claim 1, whereina height of the fibers after sliding the reticle is in a range fromabout 0.5 μm to about 0.8 μm.
 3. The method of claim 1, wherein a heightof the fibers before sliding the reticle is in a range from about 1 μmto about 1.5 μm.
 4. The method of claim 1, wherein a width of the fibersis in a range from about 0.2 μm to about 0.5 μm.
 5. The method of claim1, wherein sliding the reticle is performed such that the fibers areinclined toward the first direction.
 6. The method of claim 1, furthercomprising: sliding the reticle relative to the top surface of the chuckalong a second direction that is opposite the first direction todecrease a contact area between the fibers and the reticle.
 7. Themethod of claim 6, further comprising: detaching the reticle from thefibers after sliding the reticle relative to the top surface of thechuck along the second direction.
 8. The method of claim 1, furthercomprising: performing a photolithography process using the reticleadhered to the fibers.
 9. A method, comprising: contacting a pluralityof fibers on a top surface of a wafer holder with a wafer; and slidingthe wafer holder relative to the wafer along a first direction toincline the fibers relative to the top surface of the wafer holder, suchthat the wafer is adhered to the fibers.
 10. The method of claim 9,wherein sliding the wafer holder is performed such that a contact areabetween the fibers and the wafer increases.
 11. The method of claim 9,wherein sliding the wafer holder is performed such that a height of thefibers decreases.
 12. The method of claim 9, wherein sliding the waferholder is performed such that the fibers are inclined toward a seconddirection that is opposite the first direction.
 13. The method of claim9, further comprising: sliding the wafer holder relative to the waferalong a second direction that is opposite the first direction todecrease a contact area between the fibers and the wafer.
 14. The methodof claim 13, wherein the fibers are inclined toward the second directionwhile sliding the wafer holder relative to the wafer along the seconddirection.
 15. The method of claim 9, further comprising: detaching thewafer holder from the wafer after sliding the wafer holder relative tothe wafer along the second direction.
 16. An apparatus, comprising: aworkpiece holding device; and a plurality of bendable fibers on a topsurface of the workpiece holding device.
 17. The apparatus of claim 16,wherein a width of the bendable fibers is in a range from about 0.2 μmto about 0.5 μm.
 18. The apparatus of claim 16, wherein a height of thebendable fibers is in a range from about 1 μm to about 1.5 μm.
 19. Theapparatus of claim 16, wherein each of the bendable fibers taperstowards its top.
 20. The apparatus of claim 16, further comprising: avacuum source, wherein the workpiece holding device has a vacuum holetherein, the vacuum source is in communication with the vacuum hole ofthe workpiece holding device, and the vacuum hole of the workpieceholding device is surrounded by the bendable fibers.